The present invention relates to a liquid crystal drive method, a liquid crystal display system and a liquid crystal drive control device. The present invention relates mainly to a technique effective to be used for performing gradation display using a TFT (thin film transistor) liquid crystal display panel.
As a liquid crystal drive voltage switch method for the alternating current drive of a liquid crystal panel, the present inventors have studied a dynamic switch method and a control bit switch method prior to the present invention. FIG. 11 shows state changes at positive-negative switch in the dynamic switch method. In the dynamic switch method, display data set to each terminal cannot be changed due to positive-negative switch. A gradation generation circuit part for supplying a voltage to signal lines of a liquid crystal display panel is switched to a positive-negative level. Since display data cannot be changed due to positive-negative switch, the same selector switch is brought to the on state. In the negative phase, as indicated by the dotted lines in the drawing, voltages are switched so as to be symmetric up and down with respect to the midpoint voltage.
FIGS. 12 and 13 show state changes at positive-negative switch in the control bit switch method. In the control bit switch method, data set to each terminal is switched corresponding to positive and negative gradation voltage for the positive and negative phases. Display data having the highest order potential in the positive phase is switched to have the lowest order potential in the negative phase. An exclusive logic circuit outputs the display data as it is as logic 0 in the positive phase by a positive-negative switch signal, and inverts all or most bits of the display data as logic 1 in the negative phase. FIG. 14 shows data and selective levels of 32 gradations of 0 to 31 corresponding to the control bit switch method.